The invention relates to a door operator comprising an electric drive motor unit mechanically connected to pulling means for a single or multiple panel door by a belt drive or the like. The belt is guided positively by three pulleys. The middle pulley is a drive pulley mounted on or integral with the motor drive shaft, and the other two pulleys are guide pulleys mounted on portions of a plate located on both sides of the drive pulley and pivotable on a shaft parallel to the drive shaft. The plate, which is spring loaded toward the middle position of its pivoting range, is provided with an extension which engages switching means located in the path of plate motion.
The door operator structure is used to monitor the door panel motion in case an obstacle is present in the path of the door. The obstacle may be a vehicle, another object, or even a person. For this reason, means are provided (sometimes by law in many areas) to stop or reverse the door motion in the presence of such an obstacle.
In this case, the drive belt connected to the motor unit to transmit the drive motion to the door drive means has been guided by two pulleys around said drive pulley mounted on or integral with the motor unit output element in such a manner as to provide for a sufficiently wide loop angle for the transmission of the drive power from the drive pulley to the belt, see German Gebrauchsmuster No. 7,817,731.
Mounting of at least the guide pulleys on a plate which is pivotable about an axis located outside the output shaft axis makes it possible for the belt portion under greater load, depending on the direction of drive, to apply on its pulley a force stronger than that applied by the other belt portion on its own guide pulley. When, because of the presence of an obstacle in the path of door motion, a particularly heavy load is applied to one belt portion while the motor drive continues, the plate is deflected by the belt under heavier load and operates, by way of an extension thereof, on one of the two switches. One of these switches stops or reverses the motor, so that the door moves away from the obstacle. The other switch, arranged in the other direction of plate deflection, also provides for stopping or reversing the motor to the opposite direction of door motion or motor drive. The fact that the basic loads related to the door motion may differ in the open position and the closed position is taken into account by adjusting the switch actuator. With normal load, depending on the belt portion under load, the spring loaded plate is deflected in one or the other direction by a longer or shorter distance without actuating the switch concerned. It is only when a determined deflection value is exceeded that one of the two adjustable stops of the extension engages one or the other switch. Therefore, this accident-preventing switching arrangement is primarily responsive to the amount of deflection. This entails disadvantages because a determined amount of deflection is allowed for the normal load range, which may result in plate rocking even with weak motion resistance in the normal load range, which, at appropriate resonance, triggers the switching arrangement even in the absence of an obstacle. Consideration must be given in this connection to the load variations which are applied by variable wind pressures on the door.
For the above reasons, the threshold value for door motion inhibition should be adjustable on the basis of local conditions such as wind effects. Moreover, the door should be operable manually when the drive operation is faulty or has failed. Generally, satisfactory accessibility to the device is desirable for the easy adjustment of the above-cited safety threshold value and disconnection of the drive on failure.
Thus, an object of the invention is to provide a door drive of this type which operates exactly and separately in normal operation and accident-preventing operations, and also generally permits an improved adjustment of the actuation threshold values in response to belt tension.
The invention also relates to the adjustment of the stopping or reversing of the drive motor when an obstacle is present in the path of motion of the door with the highest possible sensitivity; and to the reduction of production costs.
Finally, another object of the invention is to provide a drive unit which requires low-maintenance, generally, and particularly relative to the adjustment of the safety threshold value.
According to the invention, the drive motor is stopped or reversed for accident prevention in the presence of an obstacle by a force-responsive value determination. The actuating elements for the switch, switch covers, or the like, which can be mounted in fixed position, are located more or less directly on either side of the extension of the pivotable plate. The springs act on both sides of the extension and their values in the inactive state are predetermined so as to be large enough that, in normal operation, a deflection of the plate will not occur that could actuate one of the switches. Only for accident prevention, i.e., when the resistance to movement is sufficiently strong and its value rises above the level indicative of an obstacle, will the drive motor be reversed or stopped. Since the adjustment can be made precise by varying the spring load, in normal operation, plate deflection practically does not occur and no rocking develops in normal operation in response to relatively small periodic disturbances in the door motion. Therefore, the drive of the invention operates faultlessly with sensitive adjustment of the threshold from which the resistance corresponding to accident prevention rises.
In another embodiment of the invention, no switch with springs is used, but a photoelectric cell is influenced by a shield when the plate is deflected in response to an obstacle, so that the beam path between the photoelectric cell transmitter and receiver is interrupted. To adjust the switching threshold value, the plate is in contact with adjustable springs whose characteristic is thus responsive exclusively to the force ratios for which the plate deflection determining the switch condition occurs. The photoelectric cell also offers the advantage that it can be operated as a normally closed contact switch, i.e., is always on, when the drive is operative. If the photoelectric cell fails or its operation is otherwise affected, the danger of the drive operating in the presence of an obstacle is avoided.
In a preferred form of this embodiment, the shield part comprises elements near the middle of the plate deflection range, on both sides of the beam path, so that always the same photoelectric cell is operated for both directions of deflection. Therefore, only one switch is needed. Basically, the beam path of the photoelectric cell can be directed perpendicularly to the plane of the plate. In another embodiment, the photoelectric cell beam path may be parallel to the plane of the plate, which, in some cases, provides for an advantage in respect to the space occupied by the structure. The structure of the shield part or shield elements is readily adaptable to this embodiment.
The springs which engage the plate on opposite sides are preferably in the form of two-armed springs pivotably mounted on a pin. The ends of the arms of said springs extending away from the plate are in contact with setscrews which are threaded into a fixed part. This fixed part is preferably the edge of the frame housing which holds the motor, the plate, and the motor-driven output pulley and can be provided with appropriate threads. Therefore, the adjustment can be effected outside the housing.
In another preferred development, the belt is in the form of a toothed belt which engages corresponding teeth of the drive pulley or motor output shaft, or of the output pulley. Thus, no problems arise in the necessary securing of the belt engagement, and the plate need not be adjusted.
The low-maintenance requirement and the device structure providing for the adjustment of the threshold value are taken into consideration by providing the housing with a housing frame component and a second component which holds the drive unit and is connected by a guide to the frame in which said housing component is movable between an operating position, in which the motor is mechanically connected to the door, and a disconnected position in which the mechanical connection is disengaged.
In the event of a malfunction in the drive unit, according to the invention, the mechanical connection of said unit with the door can be discontinued without disassembling the drive unit since the drive unit remains in the guide on disconnection and remains connected to the frame component of the housing. The shift in the guide between the operating position and the disconnected position is simple so that it can be effected by an unskilled person. Consequently, even an unskilled person can move the door manually on occurrence of a fault, without waiting for a specialist, and without the risk of damage to the mechanical connection between the door and the motor when the force is applied in the direction opposite to that of normal operation.
As a result of the shiftability of the drive unit in the guide, according to the invention, the specialist can effect repairs without disassembling the drive unit. When, at least some of the parts of the units must be changed, the unit or the intermediate housing is removed from the guides. Therefore, repair and possible prescribed maintenance are considerably simpler.
In an especially preferred embodiment of the invention, the electric power supply is interrupted when the drive is shifted in the guides for the mechanical disconnection. This provision reduces the risk of damage to the drive unit due to continued current supply in case of malfunction, and makes it possible for the specialist to conduct maintenance or repairs without risk of electrical shocks, unanticipated short circuits, or the like.
Another preferred embodiment provides for the separation of at least the mechanical connection in a first disconnection step, and then for a second disconnection step for the motor drive unit, in which the housing cover is removed. Thus, in the event of a malfunction, an unskilled person can move the door manually, and then the drive unit is made accessible to a specialist in the second disconnection step.
In still another advantageous development, the connection and/or the intermediate housing component and, optionally, also the frame component are made of elastic plastic material to avoid the transmission of vibrations, caused by the motor or the stepdown transmission, to the door acting as resonator, or the fixed portion of the housing.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.